Wafer carrier rinsing mechanism

ABSTRACT

A carrier rinse unit comprising a plurality of nozzles prepositioned to eject a cleaning fluid against a surface of a wafer while the wafer is rotated within a wafer carrier. The prepositioned nozzles may be angled to spray a leading edge, a trailing edge, an outer edge of the wafer, or any desired point on the surface of the wafer.

BACKGROUND OF THE INVENTION

[0001] 1. Technical Field

[0002] The present invention relates generally to multi-step chemicalmechanical polishing processes and, more particularly, to a wafercarrier rinsing mechanism.

[0003] 2. Related Art

[0004] Chemical-mechanical polishing (hereinafter “CMP”), is a commonmethod of planarization used in semiconductor manufacture. CMP typicallyinvolves the use of a circular polishing pad, mounted to a polishingtable or platen, which is held in contact with the surface of thesemiconductor wafer via a carrier. An abrasive slurry, typicallywater-based, is applied to the surface of the polishing pad tofacilitate and enhance polishing of the wafer. During a polishingprocess, both the polishing pad and wafer are rotated relative to oneanother. As a result, unwanted material is removed from the surface ofthe wafer, producing a planarized surface. Once complete, the wafer canbe transported to a subsequent processing step, e.g., a secondarypolishing operation, or a cleaning process.

[0005] However, after a polishing operation, residual foreign materialstend to remain on the surface of the polished wafer, which in turn canlead to cross contamination with subsequent processing steps. Becauseeach subsequent processing step can be adversely affected by residualforeign materials from a previous step, failure to adequately reducesuch contamination can lead to higher costs. Furthermore, eliminatingthe cross contamination is becoming more and more vital as the level ofprecision required for higher integrated circuit (IC) device densitiesincreases. Accordingly, a need exists for improved tools for eliminatingcross contamination in CMP processing.

SUMMARY OF THE INVENTION

[0006] The present invention provides an apparatus for removing foreignmaterials from a semiconductor wafer and wafer carrier that holds thewafer in place. The apparatus comprises a washer assembly having aplurality of propositioned nozzles for ejecting a fluid against asurface of the wafer while the carrier is rotating in order to cleanseeither/both the wafer surface and the wafer carrier. The washer assemblymay include a first plurality of nozzles positioned for spraying aleading edge of the wafer surface, a second plurality of nozzlespositioned for spraying a trailing edge of the wafer surface, and athird plurality of nozzles positioned outwardly (i.e., away from thecenter of the wafer) for forcing foreign materials towards an edge ofthe wafer surface. The washer assembly may also, for example, includenozzles that are positioned to both spray a leading edge of the waferand force foreign materials towards an edge of the wafer, oralternatively, positioned to spray a trailing edge and force foreignmaterials towards an edge of the wafer. In addition, each nozzles can bealtered to control the spray pattern associated with the nozzle.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 depicts a side view of a carrier rinse system and carrierin accordance with a preferred embodiment of the present invention;

[0008]FIG. 2 depicts an isometric view of a carrier rinse mechanism inaccordance with a preferred embodiment of the present invention;

[0009]FIG. 3 depicts a top view of a carrier rinse mechanism inaccordance with a preferred embodiment of the present invention;

[0010]FIG. 4 depicts a side view taken along section 4-4 of the carrierrinse system of FIG. 3, in accordance with a preferred embodiment of thepresent invention;

[0011]FIG. 5 depicts a cross-sectional side view taken along section 5-5of FIG. 3 in accordance with a preferred embodiment of the presentinvention;

[0012]FIG. 6 depicts a cross-sectional side view of section 6-6 of FIG.3 in accordance with a preferred embodiment of the present invention;and

[0013]FIG. 7 depicts a nozzle in accordance with a preferred embodimentof the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] Referring now to the figures, FIG. 1 depicts a wafer carrier 12being sprayed by a rinse unit 10 in accordance with the presentinvention. Wafer carrier 12 includes a wafer holder 14 and wafer 16 thatcan be rotated in the direction of arrow 15. Wafer carrier 12 can be anytype known in the art, including a WESTECH™ carrier. Rinse unit 10comprises a plurality of nozzles 18 positioned to spray a fluid 19towards wafer 16 as the wafer 16 is rotated by the wafer carrier 12.Fluid 19 is pumped from a fluid source 20 into the rinse unit 10 fordisbursement through the nozzles 18.

[0015] It is envisioned that the rinse unit 10 could be used to cleansethe wafer carrier 12 and wafer 16 after/before any of the steps commonlyutilized in a CMP process. For example, in between a primary andsecondary polishing operation, the wafer 16 could be rinsed off with therinse unit 10 in order to reduce the amount of chemicalcross-contamination. In addition, the rinse unit 10 could be used tocleanse wafer holder 14 before the wafer 16 is placed onto the waferholder 14 in order to ensure a contaminate free surface. Furthermore,the rinse unit 10 could be used after the polishing process and prior tothe cleaning process, or at any other stage where the elimination ofresidual foreign materials is desired.

[0016] It should be further recognized that the exact placement andconfiguration of nozzles 18 can be altered without departing from thescope of this invention. Moreover, it is envisioned that the inventioncould be implemented in such a manner where wafer carrier 12 couldremain stationary, while the rinse unit 10 is spun around.

[0017] Referring now to FIG. 2, an isometric view of the rinse unit 10is depicted. The rinse unit 10 comprises four nozzle banks 24, 26, 28and 30. Each of the banks comprises a plurality of nozzles 32 forejecting a spray in a direction toward the wafer carrier and wafer (notshown). The rinse unit 10 includes a base portion 34 and a plate 36. Theplate 36 is secured to the base portion 34 with screws 38 and holds thenozzles 32 in position. The rinse unit 10 is mounted on top of posts 40and 42, which are hollowed-out to provide passage of fluid into therinse unit 10. The rinse unit 10 may be mounted on a flat surface 46with nozzles pointed generally upward, or any other suitableconfiguration (e.g., horizontally or downward). The rinse unit 10comprises hollowed out passageways (not shown) for delivering fluid toeach of the nozzles 32. The rinse unit 10 may include plugs 44 at theend of each nozzle bank to provide access or closure to the hollowed-outpassageways. The rinse unit 10 may be made from any type of material,including plastic or metal, that can provide a system for mountingnozzles and delivering a fluid.

[0018] Referring now to FIG. 3, a top view of the rinse unit 10 isdepicted. As can be seen, the four nozzle banks 24, 26, 28 and 30 arearranged in an x-shape. While this embodiment depicts banks of nozzlesin an x-shape including four nozzle banks, it is understood that anynozzle layout falls within the scope of this invention. Each nozzle bankcomprises a plurality of nozzles 32. As the wafer (not shown) is rotatedabove the rinse unit 10, fluid will be pumped into each nozzle bank 24,26, 28 and 30 and through each of the nozzles 32 to remove foreignmaterial from the wafer. Each of the nozzles 32 may be angled in apredetermined direction to control the spray angle. The nozzles 32 maybe fixed (e.g., machined) to a predetermined angle, or be positionable(e.g., using bearings, etc.) by the user. Thus, the fluid being ejectedfrom each nozzle 32 in the rinse unit 10 may be directed straight up,angled in a first direction for spraying a leading edge of the wafersurface as it passes the nozzle, angled in a second direction forspraying a trailing edge of the wafer surface as it passes the nozzle,or angled outward to force foreign material towards the edge of thewafer. In addition, the nozzles can be angled in a combination ofdirections to achieve a device result. For example, the nozzles 32 canbe angled to spray toward both a leading edge of the wafer as itapproaches and towards an outside edge of the wafer. Similarly, thenozzles can be angled to spray towards a trailing edge and towards anoutside edge of the wafer. In general, each of the nozzles 32 within agiven bank of nozzles will be angled to spray in a similar direction,e.g., to spray towards a leading edge in a non-overlapping manner. Someof the various nozzle angles achievable with this invention are furtherdescribed in FIGS. 4-6.

[0019] Referring to FIG. 4, a cross-sectional side view taken alongsection 4-4 of FIG. 3 is depicted showing nozzle banks 30 and 26. Nozzlebank 30 comprises a plurality of nozzles receptors 50 that are orientedin a generally vertical direction in order to produce a vertical spraydirection. In contrast, nozzle receptors 52 are angled outward towardsthe edge of the wafer (not shown) such that as the wafer rotates foreignmaterial is forced towards an edge of the wafer surface. Also shown inFIG. 4 is passageway 48 which is used to deliver fluid to each of thenozzle receptors 50, 52. Each of the nozzle receptors includes means,such as threaded side walls, for receiving a nozzle. Alternatively, thenozzles could be integrated into the nozzle bank as a one-piece system.

[0020] Referring now to FIG. 5, a cross-sectional side view taken alongsection 5-5 of FIG. 3 is depicted. Here it can be seen that the nozzlereceptor 54 is angularly offset to the right when viewed from the centerof the rinse unit, thereby providing a spray direction suitable forspraying a leading edge of the wafer as the wafer rotates (assuming acounter-clockwise rotation). FIG. 6 depicts a cross-section of section6-6 of FIG. 3 having a nozzle receptor 56 that is angled in a leftdirection when viewed from the center of the rinse unit in order toprovide a spray direction suitable for spraying a trailing edge of thewafer as it rotates (assuming a counter-clockwise rotation).

[0021] In addition to controlling the nozzle angle, the spray patternachievable by each nozzle may likewise be altered. Referring to FIG. 7,a nozzle 58 with an aperture 60 is depicted having threading 62 formounting into a nozzle receptor. Because of the elongated shape of theaperture 60 on nozzle 58, a wide, fanned-out type spray pattern would beproduced. Thus, the user can vary the direction of the spray pattern byturning the nozzle 58 to a desired position. For example, the elongatedspray pattern could be directed in more of an up/down pattern, or moreof a left/right pattern. Moreover, the user can choose among differenttypes of nozzles (not shown) to produce a desired spray pattern (e.g.,fine, circular, etc.). Once all of the desired nozzles are installed anda direction for each nozzle is chosen, the nozzles can be locked intoposition by screwing down plate 36 on top of the base 34 (see FIG. 2).It is understood that any system for securing the nozzles in place(e.g., screw, clamp, etc.) could likewise be used.

[0022] Thus, the present invention provides enhanced spray control byallowing the user to choose: (1) the angle of the nozzle receptor, andhence the angle of the nozzle; (2) the type of nozzle, and hence theparticular spray pattern; and (3) the nozzle direction.

[0023] With this invention, a full coverage carrier rinse unit isprovided to clean a wafer insitu and carrier after each step in amulti-step CMP process. It is estimated that the rinse unit couldoperate at any pressure, but preferably will operate between 70 and 120PSI's. While this invention has been described in conjunction with thespecific embodiments outlined above, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, the preferred embodiments of theinvention set forth above are intended to be illustrative, not limiting.Various changes may be made without departing from the spirit and scopeof the invention as defined in the following claims.

1. An apparatus for removing foreign materials from a semiconductorwafer during a polishing process, comprising: a rotatable wafer carrierfor holding the wafer in place; and a washer assembly having a pluralityof prepositioned nozzles for ejecting a fluid against a surface of thewafer while the carrier is rotating in order to cleanse the surface. 2.The apparatus of claim 1 , wherein the prepositioned nozzles comprise afirst set of nozzles positioned for spraying a leading edge of the wafersurface.
 3. The apparatus of claim 2 , wherein the prepositioned nozzlescomprise a second set of nozzles positioned for spraying a trailing edgeof the wafer surface.
 4. The apparatus of claim 1 , wherein theprepositioned nozzles are grouped into a plurality of nozzle banksextending outward from a center point.
 5. The apparatus of claim 1 ,wherein the prepositioned nozzles are oriented outward in order to forceforeign materials towards an edge of the wafer surface.
 6. The apparatusof claim 1 , wherein each prepositioned nozzle generates a unique spraypattern such that the fluid from any two nozzles do not interfere witheach other.
 7. The apparatus of claim 1 , wherein the prepositionednozzles include a center nozzle that ejects fluid straight up.
 8. Acarrier rinse mechanism for cleaning a wafer supported by a wafercarrier, comprising: a first plurality of nozzle banks for ejectingfluid toward a surface of the wafer, wherein said first plurality ofnozzle banks are angled in a first direction to spray a leading edge ofthe wafer surface; and a second plurality of nozzle banks for ejectingfluid toward a surface of the wafer, wherein said first plurality ofnozzle banks are angled in a second direction to spray a trailing edgeof the wafer surface.
 9. The carrier rinse mechanism of claim 8 ,wherein a third plurality of nozzle banks are angled outward to in orderto force foreign materials towards an edge of the wafer surface.
 10. Thecarrier rinse mechanism of claim 8 , wherein a fourth plurality ofnozzle banks eject their fluid in a generally upward direction.
 11. Amethod for removing foreign materials from a wafer during a chemicalmechanical polishing process, comprising the steps of: securing thewafer in a wafer carrier; positioning the wafer carrier proximate apolishing mechanism; polishing a surface of the wafer for apredetermined time; moving the wafer carrier proximate a carrier rinseunit; rotating the wafer relative to a carrier rinse unit; and sprayingthe wafer with a fluid from the carrier rinse unit, wherein the unitincludes a first plurality of nozzle banks angled in a first directionto spray a leading edge of the wafer surface as the wafer rotates. 12.The method of claim 11 , wherein the carrier rinse unit comprises asecond plurality of nozzle banks angled in a second direction to spray atrailing edge of the wafer surface.
 13. The method of claim 11 , whereinthe carrier rinse unit comprises a third plurality of nozzle banksangled in an outward direction to spray the foreign material off an edgeof the wafer.
 14. The method of claim 11 , further comprising the steps,prior to the securing step, of: moving the wafer carrier proximate thecarrier rinse unit; and spraying the carrier with a fluid from the rinseunit.